The fundamental objective of this study is to determine the mechanism by which cholera enterotoxin and heat-labile Escherichia coli enterotoxin stimulate adenosine 3'-5'-cyclic monophosphate formation and steroidogenesis in cultured adrenal tumor cells. In the forthcoming year we plan to purify and characterize the heat-labile E. coli enterotoxin from a human strain of E. coli. The mechanism of action of E. coli enterotoxin will be compared to cholera enterotoxin and ACTH. In addition, we plan to use membrane active agents, including enzymes and phospholipids to characterize enterotoxin receptors and their relationship to adenylate cyclase. BIBLIOGRAPHIC REFERENCES: Wishnow, R.M., Lifrak, E., and Chen, C.C. Mode of action of Vibrio cholerae enterotoxin in cultured adrenal tumor cells. J. Infect. Dis., 133: S108-S114, 1976. Mundell, D.H., Anselmo, C.R., Thrupp, L.D., and Wishnow, R.M. Toxigenic Escherichia coli and childhood diarrhea. West. J. Med., 124: 357-360, 1976.